Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola

Abstract: The biomass-based air heating system was designed and developed for thermal application in value addition of agricultural produce. The system was design and developed for the thermal application in drying of grain. The system thermal application capacity, furnace capacity was determined for maximum utilization of energy in the process of drying. The quantity of air for the complete combustion of fuel required in thermal application was computed. The total heat load of the system was determined with the air required for the removal of moisture in drying of green gram. The quantification of heat losses of biomass furnace was worked out to examine the energy conservation in the combustion process. The heat losses in the furnace for the other than heating and soaking area was tapped and observed as 34.72 per cent. The furnace efficiency for indirect method was observed to be 44.87% and for direct method it was 36.74%. Based on pre-heating arrangement of feed air to heat exchanger, the fuel saving was estimated and it was found to be 24.08%. The net heat required for the thermal application of the system was computed to be 8465 kcal. The quantity of air required for drying of green gram was estimated to be 2.57kg/min. The air requirement per m2 to the total surface area of drying chamber was computed to be 0.30m3/min/m2. Based on the net fuel required volume (80 kg) of soybean briquette, for volume of 0.095m3, the furnace height was found to be 150 mm at 500 mm diameter. In design of parallel flow heat exchanger, the heat duty of the system for the fully load (16946 W/h), the LMTD of the system was found to be 74.590C. The net heat transfer area of the heat exchanger was found to be 9.87 m2. The number of tubes for the net heat transfer area (9.87 m2) was computed to be 16 with the tube diameter of 30 mm. The heat transfer coefficient was calculated to be 46.40 W/m2oK.The system was developed as per the design specification in respect of each component. The biomass-based air heating system consisted of biomass combustor equipped with pre-heating arrangement and smoke tapping unit, air distribution system and rotary tray drying bin. The power transmission system was designed and developed for rotating tray arrangement for the live and static load during the operation. The thermal energy performance of the system was worked out during the experimentation for drying of green gram. In investigation, the heat supplied by the combustor in various treatments for the set air flow rate, temperature and fuel feed rate is estimated. The heat gain by air, heat supplied to the drying bin, net heat utilized in the various treatments was estimated. The loss of heat from the combustor, in air distribution system and total system heat loss was computed in the experimentation for drying application. It was observed that maximum heat is utilized in the treatment combination of R28T65 and was 722334 KJ. The total system heat loss was found minimum in treatment combination of R14T55 and was 178217 KJ. The component wise heat loss was estimated during the operation for the treatments. The heat loss from the combustor was found to be 21833 KJ. The heat loss from the air distribution system and the dryer surface area was found to be 724 KJ and 11.83 KJ respectively. The overall energy balance for the drying is estimated during the study. The drying characteristics of green gram drying in the experiment for various treatment combination was evaluated. The performance parameters of the drying in terms of drying rate, moisture ratio, drying time was evaluated in the investigation. The effect of air flow rate and temperature on drying rate, moisture ratio, drying time was also evaluated during the experimentation. The drying rate 61.90 % is found low in treatment R14T65 over open sun drying with lowest drying time of 08 h. The moisture ratio (0.34) was found maximum in treatment R14T65. The temperature profile of the dryer bin showed that operational temperature set in the process was maintained in the dryer bin during the drying operation. The tray-wise drying rate was found uniform across all eight trays. The tray wise moisture ratio was also observed uniform across all the eight trays during drying. The thin layer drying analysis was carried out for the best suited drying model for the drying of green gram. The two-term thin layer model was best suited for the moisture ratio in many treatments for drying of green gram. The average drying efficiency was observed to be 54.11 % and highest was in treatment R28T45. The average efficiency of combustor was observed to be 56.19 % and highest was in treatment R14T65. The overall average system efficiency was found to be 30.66% and highest was observed to be 41.53% in treatment R14T65.The system and operational parameters were optimized and the operational evaluation of biomass air heating system for the thermal application was also studied on the basis of different response parameters such as drying rate, moisture ratio, combustion efficiency and drying efficiency. Similarly, system and thermal parameters were optimized and the thermal evaluation of biomass air heating system for the thermal application was also studied on the basis of different response parameters such as heat gain by air, heat supplied to bin, total system heat loss and net heat utilized. The optimized input parameter for drying rate, moisture ratio, combustor efficiency and drying efficiency were found for air flow rate of 41.77 kg/h, temperature of 650C, and fuel feed rate of 7.5 kg/h. The maximum drying rate, moisture ratio, combustor efficiency and drying efficiency was found to be 0.008, 0.339,54.41% and 59.25 %, respectively. The desirability of optimized solution was found 0.889 among the 38-solution provided in the optimization process. The optimized input parameter for heat gain by air, heat supplied to bin, total system heat loss and net heat utilized were found for air flow rate of 43 kg/h, temperature of 450C, and fuel feed rate of 4 kg/h. The heat gain by air, heat supplied to bin, total system heat loss and net heat utilized was found to be 236kWht, 226.13kWht, 54.55kWht and 176.64kWht, respectively. The desirability of optimized solution was found 0.857 among the 10 solutions provided in the optimization process. The techno-economic evaluation of the system developed was worked out for the cost of operation of drying for the temperature (OC) of 45, 55 and 65. The cost of operation (Rs/kg) for the temperature (OC) of 45, 55 and 65 were observed to be 8.6, 6.1 and 6.09, respectively for drying of green gram. The net profit (Rs/kg) for the temperature (OC) of 45, 55 and 65 were observed to be 3.15, 5.65 and 5.66, respectively for drying of green gram. The economical feasibility of the system for drying of green gram was worked out using the discounted cash flow technique. The net present worth was found positive for the temperature (OC) of 45, 55 and 65 and therefore investment in the project is feasible. The benefit cost ratio was found for the temperature (OC) of 45, 55 and 65 is 1.30, 1.83 and 1.83, respectively. The internal rate of return (%) was found for the temperature (OC) of 45, 55 and 65 as 19.80, 35.20 and 35.70, respectively. The all economical parameters evaluated showed that investment in project of biomass air heating system is feasible in perspective of business utility.

Dr. Panjabrao Deshmukh Krishi Vidyapeeth, Akola

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